(one of) the greatest shareware successes of all time

- Doom -
"If you are having trouble going online to take this game to the next level of entertainment, it's probably because you stole the copy you're playing. That's OK - you know, now would be an excellent time to decide to buy a genuine copy. You got one over on us, took our hard work and got a free ride - looks like you're enjoying it so far; glad you like the game :) - but we really would appreciate it if you did us this little favor, and helped us pay our employees for all their hard work."

via Gamasutra